Integrated circuit switches used in 3D and other integrated circuits can be formed from solid state structures (e.g., transistors) or passive wires (MEMS). MEMS switches are typically employed because of their almost ideal isolation, which is a critical requirement for wireless radio applications where they are used for mode switching of power amplifiers (PAs).
MEMS can be manufactured in a number of ways using a number of different tools. In general, though, the methodologies and tools are used to form small structures with dimensions in the micrometer scale. Also, many of the methodologies, i.e., technologies, employed to manufacture MEMS have been adopted from integrated circuit (IC) technology. For example, almost all MEMS are built on wafers and are realized in thin films of materials patterned by photolithographic processes. More specifically, the fabrication of MEMS use three basic building blocks: (i) deposition of thin films of material on a substrate, (ii) applying a patterned mask on top of the films by photolithographic imaging, and (iii) etching the films selectively to the mask.
Depending on the particular application and engineering criteria, MEMS structures can come in many different forms. For example, MEMS can be realized in the form of a single cantilever structure such as, for example, shown in U.S. Pat. No. 5,578,976. In this cantilever application, a single cantilever arm (suspended electrode) is pulled toward a fixed electrode by application of a voltage. To manufacture such a cantilever structure, though, several extra and expensive processing steps are required, in addition to the building of the CMOS structure itself. For example, once all of the CMOS wiring is completed, additional processes steps are required to form the MEMS switch, which adds considerable processing costs to the structure.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.